VHS: Map

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Video Home System, better known by its
abbreviation VHS, is a video tape recording
standard developed during the 1970s. It was released to the public
during the latter half of the decade. During the late part of the
1970s and the early 1980s it formed one-half of the VHS vs Betamax war, which VHS would
eventually go on to win. VHS' properties include longer playing
time, faster rewinding and fast-forwarding, and a less complex tape
transport mechanism. The open standard
used for VHS technology allowed mass production without licensing
costs. VHS would eventually come out as the winning video tape
format, surpassing other home tape formats by the 1990s.

In later years, optical disc formats
began to offer better quality than video tape, and took over in
film studios, then retailers, and finally video rental stores.
By 2006,
the United
States had stopped releasing new movie titles in VHS
format, opting for others such as DVD and
Blu-ray. On December 31, 2008, the
last major United States supplier of pre-recorded VHS tapes,
Distribution Video Audio Inc. of Palm Harbor, Florida, shipped its
final truckload.

Technical details

Video recording

A VHS cassette holds a maximum of about 430 m of tape at the
lowest acceptable tape thickness, giving a maximum playing time of
about 3.5 hours for NTSC and 5 hours for PAL at "standard" (SP)
quality. Other speeds include LP and EP/SLP which double and triple
the recording time, for NTSC regions. These speed reductions cause
a slight reduction in video quality (from 250 lines to 230 analog
lines horizontal); also, tapes recorded at the lower speed often
exhibit poor playback performance on recorders other than the one
they were produced on. Because of this, commercial prerecorded
tapes were almost always recorded in SP mode.

VHS tapes have approximately 3 MHz of
video bandwidth, which
is achieved at a relatively low tape speed by the use of helical scan recording of a frequency modulated luminance (black
and white) signal, with a down-converted "color
under" chroma (color) signal
recorded directly at the baseband. Because VHS is an analog system,
VHS tapes represent video as a continuous stream of waves, in a
manner similar to analog TV broadcasts. The waveform per scan-line
can reach about 160 waves at max, and contains 525 scanlines from
top of the screen to bottom of the screen in NTSC (480 visible). PAL variants have 625 scanlines
(576 visible). In modern-day digital terminology, VHS is roughly
equivalent to 333x480 pixels.

JVC would counter 1985's SuperBeta with VHS HQ, or High Quality.
The frequency modulation of the VHS luminance signal is limited to 3 megahertz
which makes higher resolutions impossible, but an HQ branded deck
includes luminance noise reduction, chroma noise reduction, white
clip extension, and improved sharpness circuitry. The effect was to
increase the apparent horizontal resolution of a VHS recording from
240 to 250 analog (equivalent to 333 pixels from left-to-right, in
digital terminology). The major VHS OEM resisted HQ due to cost
concerns, eventually resulting in JVC reducing the requirements for
the HQ brand to white clip extension plus one other
improvement.

In 1987 JVC introduced the new format called Super VHS which
extended the bandwidth to over 5 megahertz, yielding 420 analog
horizontal (560 pixels left-to-right).

Audio recording

In the original VHS format, audio was recorded as baseband in a single linear track, at the upper
edge of the tape, similar to how an audio compact cassette operates. The recorded
frequency range was dependent on the movement of the tape past the
audio head, which for the VHS SP mode, resulted in a mediocre
frequency response of roughly 100 Hz to 10 kHz. The signal-to-noise ratio was an
acceptable 42 dB. Both parameters degraded significantly with VHS's
longer play modes, with EP frequency response peaking at
4 kHz.

More expensive decks offered stereo audio recording and playback.
Linear stereo, as it was called, fit two independent channels in
the same space as the original mono audiotrack. While this approach
preserved acceptable backward compatibility with monoaural audio
heads, the splitting of the audio track degraded the signal's SNR
to the point that audible tape hiss was objectionable at normal
listening volume. To counteract tape hiss, decks applied Dolby B noise reduction for
recording and playback. Dolby B dynamically boosts the
mid-frequency band of the audio program on the recorded medium,
improving its signal strength relative to the tape's background
noise floor, then attenuates the mid-band during playback. Dolby B
is not a transparent process, and Dolby-encoded program material
will exhibit an unnatural mid-range emphasis when played on
non-Dolby capable VCRs.

High-end consumer recorders took advantage of the linear nature of
the audio track, as the audio track could be erased and recorded
without disturbing the video portion of the recorded signal. Hence,
"audio dubbing" and "video dubbing", where either the audio or
video are re-recorded on tape (without disturbing the other), were
supported features on prosumer editing-decks. Without dubbing
capability, an audio or video edit could not be done in-place on
master cassette, and requires the editing output be captured to
another tape, incurring generational loss.

Studio film releases began to emerge with linear stereo audiotracks
in 1982. From that point onward nearly every home video releases by
Hollywood featured a Dolby-encoded linear stereo audiotrack.
However, linear stereo was never popular with equipment makers or
consumers.

Around 1985, JVC added Hi-Fi audio to VHS (in response to
Betamax's introduction of Beta Hi-Fi.) Both VHS Hi-Fi and Betamax
Hi-Fi delivered flat full-range frequency response (20 Hz to
20 kHz), excellent 70 dB signal-to-noise ratio (in consumer
space, second only to the compact
disc), dynamic range of 90 dB, and
studio-grade channel separation (more than 70dB). VHS Hi-Fi audio
is achieved by using audio frequency modulation (AFM), recording
each of the 2 stereo channels (L, R) on a frequency-modulated
carrier and embedding the modulated audio signal pair into the
video signal. To avoid crosstalk and interference from the primary
video carrier, VHS's implementation of AFM relied on a form of
magnetic recording called depth multiplexing. The modulated audio carrier pair was placed under the
luminance carrier (below 1.6 MHz), and recorded first.
Subsequently, the video head erases and re-records the video signal
over the same tape surface, but video signal's higher center
frequency results in a shallower magnetization of the tape,
allowing both the video and residual AFM audio signal to coexist on
tape. (PAL versions of Beta Hi-Fi use this same technique). During
playback, VHS Hi-Fi recovers the depth-recorded AFM signal by
subtracting the audio head's signal (which contains the AFM signal
contaminated by a weak image of the video signal) from the video
head's signal (which contains only the video signal), then
demodulates the left and right audio channels from their respective
frequency carriers. The end result of the complex process was audio
of outstanding fidelity, which was uniformly solid across all
tape-speeds (EP or SP.) Since JVC had gone through the complexity
of ensuring Hi-Fi's backward compatibility with non-Hi-Fi VCRs,
virtually all studio home video releases contained Hi-Fi
audiotracks (in addition to the linear audio track). Under normal
circumstances, all Hi-Fi VHS VCRs will record Hi-Fi and linear
audio simultaneously to ensure compatibility with VCRs without
Hi-Fi playback, though only early, high-end Hi-Fi machines provided
linear stereo compatibility.

The sound quality of Hi-Fi VHS stereo is comparable to the quality
of CD audio, particularly when recordings were made on high-end or
professional VHS machines that have a manual audio recording level
control. This high quality compared to other consumer audio
recording formats such as compact
cassette attracted the attention of amateur and hobbyist
recording artists. Home recording
enthusiasts occasionally recorded high quality stereo mixdowns and master
recordings from multitrack audio tape
onto consumer-level Hi-Fi VCRs. However, because the VHS Hi-Fi
recording process is intertwined with the VCR's video-recording
function, advanced editing functions such as audio-only or
video-only dubbing are impossible. Some VHS decks also had a
"simulcast" switch, allowing users to record an external audio
input along with off-air pictures. Some televised concerts offered
a stereo simulcast soundtrack on FM radio and as such, events like
Live Aid were recorded by
thousands of people with a full stereo soundtrack despite the fact
that stereo TV broadcasts were some years off (especially in
regions that adopted NICAM).

The considerable complexity and additional hardware limited VHS
Hi-Fi to high-end decks for many years. While linear stereo all but
disappeared from home VHS decks, it was not until the 1990s that
Hi-Fi became a more common feature on VHS decks. Even then, most
customers were unaware of its significance and merely enjoyed the
better audio performance of the newer decks.

Cassette and tape design

Bottom view of VHS cassette with
magnetic tape exposed

Top view of VHS cassette with front
casing removed

The VHS cassette is a 187 mm wide, 103 mm deep,
25 mm thick (7⅜" × 4" × 1") plastic clamshell held together
with five Phillips head screws. The
flip-up cover that protects the tape has a built-in latch with a
push-in toggle on the right side (see bottom view image). The VHS
cassette also includes an anti-despooling mechanism as seen in the
top view, several plastic parts near front label end of the
cassette between the two spools. The spool brakes are released by a
push-in lever within a 6.35 mm (1/4") hole accessed from the
bottom of the cassette, about 19.05 mm (3/4") in from the edge
label.

There is a clear tape leader at both ends of the tape to provide an
optical auto-stop for the VCR transport mechanism. A light source
is inserted into the cassette (through the circular hole in the
center of the underside) when loaded in the VCR, and two photodiodes are located to the left and right
sides of where the tape exits the cassette - when the clear tape
reaches one of these, enough light will pass through the tape to
the photodiode to trigger the stop function, or in more
sophisticated machines it will start rewinding the cassette when
the trailing end is detected. Early VCRs used an incandescent bulb as the light source,
which can fail and may cause the VCR to erroneously think that a
cassette is loaded when empty, or will detect the blown bulb and
stop functioning completely. Later designs use an infrared LED which has a much longer
lifetime.

The recording medium is a 12.7 mm (½ inch) wide magnetic tape wound between two spools,
allowing it to be slowly passed over the various playback and
recording heads of the video
cassette recorder. The tape speed is 3.335 cm/s for
NTSC, 2.339 cm/s for PAL.

VHS M-loading system.

As with almost all cassette-based videotape systems, VHS machines
pull the tape from the cassette shell and wrap it around the
head drum. VHS machines, in contrast to
Betamax and Beta's predecessor U-matic, use an "M-loading" system, also known as
M-lacing or omega wrap, where the tape is drawn out by two
threading posts and wrapped around more than 180 degrees of the
head drum (and also other tape
transport components) in a shape roughly approximating the
letter M.

Tracking adjustment and index marking

Another linear control track, at the tape's lower edge,
holds pulses that mark the beginning of every frame of video; these
are used to fine-tune the tape speed during playback and to get the
rotating heads exactly on their helical tracks rather than having
them end up somewhere between two adjacent tracks (a feature called
tracking). Since good tracking depends on the exact
distance between the rotating drum and the fixed control/audio head
reading the linear tracks, which usually varies by a couple of
micrometers between machines due to manufacturing tolerances, most
VCRs offer tracking adjustment, either manual or automatic, to
correct such mismatches. The control can additionally hold
index marks. These are normally written at the beginning
of each recording session, and can be found using the VCR's
index search function: this will fast-wind forward or
backward to the nth specified index mark, and resume
playback from there. There was a time when higher-end VCRs provided
functions for manually removing and adding these index marks — so
that, for example, they coincide with the actual start of the
program — but this feature has become hard to find in recent
models.

By the late 1990s, some high-end VCRs offered more sophisticated
indexing. For example, Panasonic's Tape
Library system assigned an ID number to each cassette, and logged
recording information (channel, date, time and optional program
title entered by the user) both on the cassette and in the VCR's
memory for up to 900 recordings (600 with titles).

Variations

VHS-C adapter

Super-VHS / Digital-VHS (high-definition) / ADAT

Several improved versions of VHS exist, most notably Super-VHS , an analog video standard with improved
video bandwidth. S-VHS improved the luminance resolution to 400
horizontal per picture height (versus 250 for VHS/Beta and 500 for
DVD). The audio-system (both linear and AFM) is the same. S-VHS
made little impact on the home market, but gained dominance in the
camcorder market due to its superior picture quality.

The ADAT format provides the ability to record
multitrack digital audio using S-VHS media.

The other improved standard, called Digital-VHS , records digital high definition video
onto a VHS form factor tape. D-VHS can record up to 4 hours of ATSC
Digital Television in 720p or 1080i formats using the fastest
record mode (equivalent to VHS-SP), and up to 40 hours of standard
definition video at slower speeds.

VHS-C / Super VHS-C

Another variant is VHS-Compact , originally
developed for portable VCRs in 1982, but ultimately finding success
in palm-sized camcorders. Since VHS-C
tapes are based on the same magnetic tape as full size tapes, they
can be played back in standard VHS players using a mechanical
adapter, without the need of any kind of signal conversion. The
magnetic tape on VHS-C cassettes is wound on one main spool and
uses a gear wheel to advance the tape; the longest tape available
holds 40 minutes in SP mode and 120 minutes in EP mode.

Super VHS or S-VHS was developed by JVC in 1987. S-VHS provided an improved luminance and
chrominance quality, yet S-VHS recorders were compatible with VHS
tapes.

Sony Betamax was unable to shrink that form any further, so instead
they developed Video8/Hi8 which was in direct competition with the
VHS-C/S-VHS-C format throughout the 80s, 90s, and 2000s. Ultimately
neither format "won" and both continue to be sold in the low-end
market (examples: JVC SXM38 and Sony TRV138). Super VHS-C camera
recordings can be played back in standard VHS VCRs with SVHS-ET
technology.

HP also developed a backup system that used VHS tapes known
internally as Hero, storing up to 5 GB per tape. It was cancelled
in 1987 as it was quickly overtaken by DAT tapes which became
available at similar storage capacity and smaller physical
size.

W-VHS

W-VHS allowed recording of MUSE Hi-Vision
analog high definition television, which was broadcast in Japan
from 1989 until 2007.

D9

There is also a JVC-designed component digital professional
production format known as Digital-S, or officially under the name
D9, that uses a VHS form factor tape and essentially the same
mechanical tape handling techniques as an S-VHS recorder. This
format is the least expensive format to support a pre-read edit.
This format is most notably used by Fox for some of its cable
networks.

Signal standards

VHS can record and play back all varieties of analog television signals in
existence at the time VHS was devised. However, a machine must be
designed to record a given standard. Typically, a VHS machine can
only handle signals of the country it was sold in. The following
signal varieties exist in conventional VHS:

PAL/576/25 (most of Western Europe,
Australia, many parts of Asia such as China and India, some parts
of South America such as Argentina, Uruguay and the Falklands, and
Africa)

Since the 1990s, dual- and multi-standard VHS machines have become
more and more common. These can handle VHS tapes of more than one
standard. For example, regular VHS machines sold in Australia and
Europe nowadays can typically handle PAL, MESECAM for record and
playback, plus NTSC for playback only. Dedicated multistandard
machines can usually handle all standards listed, some high end
model can even convert a tape from one standard to another by using
a built-in standards converter.

S-VHS only exists in PAL/625/25 and NTSC/525/30. S-VHS machines
sold in SECAM markets record internally in PAL, and convert to/from
SECAM during record/playback, respectively. Likewise, S-VHS
machines for the Brazilian market record in NTSC and convert
to/from PAL-M.

A small number of VHS decks are able to decode closed captions on pre-recorded video
cassettes. A smaller number still are able, additionally, to record
subtitles transmitted with world standard
teletext signals (on pre-digital services),
simultaneously with the associated program.

Tape lengths

Both NTSC and PAL/SECAM VHS cassettes are physically identical
(although the signals recorded on the tape are incompatible).
However, as tape speeds differ between NTSC and PAL/SECAM, the
playing time for any given cassette will vary accordingly between
the systems.

In order to avoid confusion, manufacturers indicate the playing
time in minutes that can be expected for the market the tape is
sold in. It is perfectly possible to record and play back a blank
T-XXX tape in a PAL machine or a blank E-XXX tape in an NTSC
machine, but the resulting playing time will be different from that
indicated. SP is Standard Play and LP is Long Play at 1/2 speed for
both NTSC and PAL regions. EP/SLP designates Extended Play/Super
Long Play at 1/3rd speed for NTSC regions.

E-XXX indicates playing time in minutes for PAL or SECAM in SP
speed.

T-XXX indicates playing time in minutes for NTSC or PAL-M in SP
speed.

Common Tape Lengths in minutes
(hours)

Tape Label

Tape Length

Rec. Time (NTSC)

Rec. Time (PAL)

m

ft

SP

LP

EP/SLP

SP

LP

T-120

247.5

812

120 min (2 h)

240 min (4h)

360 min (6h)

169 min (2:49 h)

338 min (5:38 h)

T-180

368.8

1210

180 min (3 h)

360 min (6 h)

540 min (9 h)

253 min (4:13 h)

507 min (8:27 h)

T-210 (rare)

433.1

1421

210 min (3:30 h)

420 min (7 h)

630 min (10:30 h)

294 min (4:56 h)

592 min (9:52 h)

DF480 (T-240 equiv)

495

1624

240 min (4 h)

480 min (8 h)

720 min (12 h)

340 min (5:40 h)

680 min (11:20 h)

E-120

173.7

570

83 min (1:26 h)

172 min (2:52 h)

258 min (4:18 h)

120 min (2 h)

240 min (4 h)

E-180

259.4

851

129 min (2:09 h)

258 min (4:18 h)

387 min (6:27 h)

180 min (3 h)

360 min (6 h)

E-240

348.1

1142

173 min (2:53 h)

346 min (5:46 h)

519 min (8:39 h)

240 min (4 h)

480 min (8 h)

Uses in marketing

Although VHS was a popular delivery format for long-play content,
VHS was also used to deliver short-play content, such as music
videos, in-store videos and tutorials.

VHS single

VHS single, also known as videotape single or
Video 45s (a play on the term "45" when used to describe
vinyl records), is a music single, using a standard-sized VHS
cartridge. The format has existed since the early 1980s. In 1983,
British synthpop band The Human League released the UKs first
commercial video single called "The Human League Video
Single". It wasn't a huge commercial success due to the high
retail price of £10.99, compared to £1.99 for a vinyl single.

The VHS single format gained higher levels of mainstream popularity
when Madonna released
"Justify My Love" as a video single
in 1990 following the blacklisting of the video by MTV. U2 also released "Numb", the lead
single from their 1993 album Zooropa as a video single.

Despite the success of these releases, the video single struggled
as its releases were relatively periodical, the technology slowly
being superseded first by music CDs with computer-accessible video
files, then, by the early 2000s, by both DVD
singles and CD+DVD releases.

Other uses

VHS was also commonly included in various products and services -
including exercise equipment, kitchen appliances, and even computer
software. Corporations used the VHS format to deliver addresses
made by company executives to regional offices. Manufacturers would
send out VHS tapes to its service centers, to demonstrate how to
repair a new product. And, retail stores would play VHS tapes
demonstrating a product on a television set, requiring a VCR that
supported encore function replay or auto rewind
play.

VHS vs. Betamax

MII, VHS, and S-VHS are distinct from
above...

...the undersides are more
similar.

VHS was the winner of a protracted and somewhat bitter format war
during the late 1970s and early 1980s against Sony's Betamax format.

Betamax was widely perceived at the time as the better format, as
it offered a slightly higher vertical resolution (250 lines vs. 240
lines in PAL & NTSC), lower video noise, and less luma-chroma
crosstalk than VHS, and was
marketed as providing pictures superior to VHS's, however the
introduction of B-II speed (2-hour mode) to compete with VHS's
2-hour Standard Play mode, reduced Betamax's vertical resolution to
240 lines. The extension of VHS to VHS HQ produced 250 lines, so
that overall a Betamax/VHS user could expect virtually identical
luminance and chrominance resolution (~30 lines across), wherein
the actual picture performance depended on other factors, including
the condition and quality of the videotape, and the specific video
recorder machine model.

Betamax held an early lead in the format war — but by 1981, U.S.
Betamax sales had sunk to only 25% of all sales.

Slow decline

The VHS VCR was a mainstay in the TV-equipped living room for more
than a decade, but is being replaced by newer technologies. For
time-shifting (off the air or cable/satellite taping), hard-drive
based DVRs have replaced the VCR as the time-shifting device of
choice, especially in households with subscriber-based TV-services.
The home camcorder market, one which VHS shared with alternative
formats, has already transitioned to digital-video recording. But
the largest blow to VHS was the March 1997 introduction of the DVD
format to American consumers. For home-video (that is, pre-recorded
commercially-released movies, etc.) rental and sales, DVD has completely taken the place of VHS.

At most electronics retailers, choice among VHS equipment is
increasingly shrinking. New sales are focused on DVD-recorders and
subscriber-based DVRs (such as TiVo). Most
electronics chains have stopped stocking VHS home-video releases,
focusing only on DVD and Blu-ray Disc technology. Major Hollywood
studios no longer issue releases on VHS. The final major Hollywood
motion picture released on VHS was David Cronenberg's A History of Violence.
However, home-video VHS tapes can still be found in many
second-hand shops, and are sometimes very cheap due to the lack of
demand.

On December 31, 2008, the final truckload in the USA of recorded
programming on VHS tapes rolled out of a warehouse owned by Ryan
Kugler, the last major supplier of VHS-recorded videos. Kugler is
President and co-owner of Distribution Video Audio, a seller of
distressed goods such as VHS tapes. According to Kugler, "It's
dead, this is it, this is the last Christmas, without a doubt. I
was the last one buying VHS and the last one selling it, and I'm
done. Anything left in warehouse we'll just give away or throw
away."

Although VHS has quickly faded from mainstream home-video, the VCR
is still used in many US households. The Washington Post noted that
as of 2005, 94.5 million Americans still owned VHS format
VCRs.

The last standalone JVC VHS-only unit was produced on December 31,
2008. JVC, like many other manufacturers, still makes combination
DVD+VHS units.

Several retail chains in the United States and in Europe planned to
stop selling VHS equipment in 2004, 2005, and 2006. Despite these
plans, VHS recorders and blank tapes are still being sold in major
stores worldwide. As an acknowledgment of VHS popularity, in 2009
Panasonic has announced the world’s first dual deck VHS-Blu-ray
player.

Successors

DVD

The DVD-Video format was introduced first,
in 1996, in Japan, to the United States in March 1997 (Test
Marketed) and mid-late 1998 in Europe and Australia.

Despite DVD's better quality (480 typical versus 250 lines
horizontal resolution), VHS is still widely used in home recording
of television programs due to the large installed base and the
lower cost of VHS recorders and tape. The commercial success of DVD
recording and re-writing has been hindered by a number of factors
including:

A reputation for being temperamental and unreliable, as well as
the risk of scratches and hairline cracks.

Incompatibilities in playing discs recorded on a different
manufacturer's machines to that of the original recording
machine.

Shorter recording time: Up to six hours on a single-layer disc
(with high compression) versus approximately 12 hours on a T-240 or
DF420 tape.

Compression artifacts: MPEG-2 video
compression can result in visible artifacts such as macroblocking, mosquito noise and ringing which become accentuated in
extended recording modes (more than three hours on a DVD-5 disc). Standard VHS will also result in reduced
luminance resolution which will make the picture look horizontally
blurred (resolution decreases further with LP and EP recording
modes).

Blu-ray Disc

A newer optical disc format is Blu-ray
Disc, which is the designed successor to DVD. A single Blu-ray Disc can hold up to 50GB (over 5X the
memory of DVD) of information including up to 1080pHigh-definition
video, high definition photos, music, and more.

High-capacity digital recording technologies

High-capacity digital recording systems are also gaining in
popularity with home users. These types of systems come in several
form factors:

Hard disk-based systems include TiVo as well as
other digital video recorder
offerings. These types of systems provide users with a
no-maintenance solution for capturing video content. Customers of
subscriber-based TV generally receive electronic program guides,
enabling one-touch setup of a recording schedule. Hard disk-based
systems allow for many hours of recording without user-maintenance.
For example, a 120 GB system recording at
an extended recording rate (XP) of 10 Mbit/sMPEG-2 can
record over 25 hours of video content.